IEEE sections 802.11, 802.11(a), 802.11(b), 802.11(g), 802.11(h), 802.11(n), 802.16, 802.20, which are hereby incorporated by reference, define ways for configuring wireless Ethernet networks and devices. According to these standards, a wireless Ethernet network device may operate in either an ad-hoc mode or an infrastructure mode. In the ad-hoc mode, as shown in FIG. 1, each client station 10-1, 10-2, . . . , and 10-N (collectively client stations 10) communicates directly with other client stations without requiring an access point (AP). In the infrastructure mode, as shown in FIG. 2, each client station 20-1, 20-2, . . . , and 20-M (collectively client stations 20) communicates with other client stations through an AP 24. The AP 24 may provide a connection to a network 26, a server 28, and for the Internet 30.
In the infrastructure mode, the AP 24 and the client station(s) 20 that use the AP 24 constitute a basic service set or BSS. A wireless Ethernet network can comprise multiple BSS's. Each BSS is identified by a unique identifier for the AP in the BSS, called a BSSID. An AP transmits a beacon, that is, a packet or a frame of information, to inform the client stations in the BSS that the AP is ready to communicate with the client stations. A beacon includes the BSSID, a beacon interval, and a delivery traffic indication message (DTIM).
A beacon interval specifies the period of time between scheduled beacons. Based on the beacon interval, the client stations can determine the duration of time that they can sleep, or wait in low-power mode, before waking up to handle the next beacon and either receive the data from or transmit the data to the AP. The beacon intervals are programmable. The DTIM in a beacon contains a DTIM count and a DTIM period. The DTIM count indicates the number of beacon intervals prior to the next DTIM beacon and the DTIM period indicates the number of beacon intervals between successive DTIMs.
An AP schedules a beacon for transmission at a target beacon transmission time (TBTT). Immediately following a beacon transmission of type DTIM, the AP transmits the broadcast and multicast frames to client stations using normal transmission rules.
FIG. 3 shows a typical system on chip (SOC) circuit 40 that can be used to implement a wireless Ethernet network device, that is, a client station and/or an AP. The SOC 40 generally includes one or more processors 42, such as an advanced RISC machine or ARM processor; a medium access controller (MAC) device 44; a baseband processor (BBP) 46; and a host interface, such as a peripheral component interface (PCI) (not shown). Additionally, the SOC 40 may include a radio frequency (RF) transceiver 48 or the transceiver may be located externally.